The present invention relates generally to a load sharing control system that enables load sharing in the case of forwarding packets in an IP (Internet Protocol) network, and more particularly to a wide area load sharing control system that enables packets to be forwarded with a high quality in a large-scale label switching network.
Traffic engineering (which will hereinafter abbreviated to TE in some cases) is a technique for performing wide area load sharing in the IP network. This traffic engineering is a technical concept aiming at avoiding congestion in the network or efficiently utilizing network resources by forwarding the packets via a plurality of routes in a way that does not stick to the route determined by an existing routing protocol (routing algorithm). MPLS (Multiprotocol Label Switching) is a protocol used for build a network architecture in which the TE is concretely conducted.
MPLS enables a packet attached with a fixed-length label to be forwarded across a preset-up connection known as LSP (Label Switched Path). According to MPLS, the traffic control using paths on the IP network can be attained by extending (setting up or establishing) the LSPs along on a route obtained by an IP-based routing protocol.
Further, MPLS enables the set-up of the paths independent of the existing IP routing, and therefore the traffic engineering (TE) can be performed by utilizing these paths. One example thereof is wide area load sharing control involving the use of a plurality of LSPs.
The load sharing control is defined as a technique for distributing an input traffic to ingress edge routers to a plurality of paths by setting up these paths in an intra-network traffic engineering section, i.e., between the ingress edge routers (nodes) that execute the TE and egress edge routers. It is possible to avoid the load from concentrating on a single route, improve a resource usage efficiency in the whole network and avoid a long-term congestion by adopting this load sharing control technique.
Another load sharing control technique involve adopting such a control method that a scheme is not that the plurality of paths are set up from the beginning but that a load state of the traffic in the network is monitored at all times and, when a load on a certain route increases, a new path is established by searching for a different route directed to the same destination.
What has generally been proposed so far in order to execute the TE-based wide area load sharing is to install (a) a statistic information gathering function, (b) a route calculating (route searching) function and (c) a load sharing calculating function (algorithm) into the respective edge routers in the MPLS-based label switching network. Namely, each of the edge routers operates autonomously distributively the functions necessary for the TE.
This autonomous distribution type traffic engineering has requires, in (a) the statistic information gathering function, a creation of a special message by which all the routers (edge routers and core routers) notify each edge router of the self-router statistic information (traffic information). This message format is not yet standardized. Hence, there is a case where the routers in the network can not send and receive the message, and there arises a problem in which a flexibility of building the network might be lost.
Further, according to the autonomous distribution type TE, if all the functions (a) through (c) are executed in the edge routers, it can be considered that a processing performance declines due to a rise in a CPU load of the router concerned. In particular, the router generally uses a large quantity of CPU resources for a packet forwarding process, a routing protocol process and so on, and hence it is inevitable that a performance of the essential function of the router declines because of executing the traffic engineering (TE) process.
Moreover, the functions (a) through (c) and the routing protocol process come to have a higher processing load with a larger number of routers in the network. Accordingly, in the autonomous distribution type TE by the edge routers, a scale-up of the network is difficult to attain.